A given cellular communications system typically includes a base transceiver station (BTS) that provides service to one or more mobile stations within the coverage area of the BTS. The BTS may include a radio antenna system having one or more antennas mounted on a tower. A given antenna may transmit downlink signals to and/or receive uplink signals from mobile stations serviced by the BTS. Further, the radio antenna system may also include a tower-top low-noise amplifier (TTLNA) and feedline system (collectively, a receive signal path). The TTLNA amplifies signals received from the antenna (i.e., uplink signals), and the feedline system is used to transmit an amplified signal from the tower top to the BTS location at the base of the tower.
It is standard practice to calibrate and otherwise validate the integrity of the TTLNA and feedline system. This may be accomplished by injecting a wideband noise signal of known characteristics into the TTLNA at the top of the tower, and then reading the characteristics of the transported signal at the BTS location at the base of the tower. This diagnostic procedure may help determine the gain of the TTLNA, the loss of the feedline system, and other information about the radio antenna system. If the signal received at the BTS location does not conform to the original engineering design specifications for the radio antenna system, then the TTLNA gain may be adjusted and/or feedline system may be repaired or replaced accordingly.
To inject a wideband noise signal of known characteristics into the TTLNA at the top of the tower, a test signal or noise source is required. However, current practice may require a technician to physically climb to the top of the tower with test equipment to inject the wideband noise signal into the TTLNA. Requiring a technician to climb to the top of the tower may be labor intensive, time-consuming, and dangerous. Alternatively, an additional feedline may be run from the TTLNA to the base of the tower or BTS location. The additional feedline allows these tests to be run without requiring a technician to climb to the tower top. Although saving a tower climb, this diagnostic procedure has several disadvantages. For instance, the additional feedline (i) is an additional installation expense, (ii) is an additional weight load on the tower, (iii) is an additional monthly lease expense, and (iv) can develop faults of its own, thereby incorrectly indicating a problem in the radio antenna system. Further, a technician must travel to the tower top to attach the additional feedline to the TTLNA.